Many applications in which electronic circuits are used require the generation of signals related to physical parameters, such as, position, angle, velocity, acceleration, temperature, pressure, force, strain, luminosity, and fluid flow rate. Where the size and the cost of the electronic circuits are not of paramount importance, these parameters may be sensed with large scale transducers that generate analog signals. These analog signals may be connected to analog circuits for processing. Some analog signal processing circuits have been implemented within integrated circuits. The transistors in these analog circuits require substantially longer channels and consume more power than transistors in digital circuits. Digital transistors cannot be used to process these analog signals because they do not operate with precise linearity over the range of the analog signals. Consequently, the analog circuits for processing the analog signals representing physical parameters cannot be miniaturized to the extent that digital circuits can be miniaturized.
Technological advances have enabled some of these physical parameters to be measured fairly accurately with the use of monolithic integrated and micro electromechanical systems (MEMS). The physical responses of these systems may be converted to analog signals. These signals, however, require conversion to digital signals before they can be connected to digital signal processing circuits that are comprised of digital transistors. These digital transistors are close to the minimum feature size possible with known fabrication processes. As used in this document, “minimum transistors” refer to minimum feature size transistors that are typically used for digital signal processing. These transistors usually consume less power when operated than transistors in typical analog signal circuits. “Minimum” refers to the size of a transistor and the power consumption for the transistor during its operation. “Analog transistors” refers to transistors having long channel lengths that are useful for analog signal processing. These transistors typically consume more power than minimum transistors. Typically, the ratio of analog transistor channel lengths to minimum transistor channel lengths is approximately 10:1. Size, weight, cost, and power consumption of circuits for processing signals from sensors are very important issues, especially when the sensors are embedded ubiquitously in an environment. Low cost sensor modules, which are small, accurate, reliable, and easily interfaced with other control circuits for an application, are desirable.